Effects of pollution on human health
Most of this section will focus on the effects of water pollution, but we should not forget air pollution. Air pollutants in the form of dust and soot (particulate matter) and gases such as carbon monoxide, sulphur dioxides and nitrogen oxides have serious impacts on health. Intense air pollution causes reduced lung function and diseases of the respiratory system such as asthma and bronchitis. The direct causal link is difficult to prove, but air pollution from domestic fires and vehicle emissions is a likely contributory factor. We now turn to the significant impacts on health from water pollution.
Children in developing countries have frequent diarrhoea episodes before the age of five. What could be the cause of these illnesses in children? What other factors might have been involved in transmitting these illnesses?
Ingesting contaminated water and food is the cause of diarrhoea. Poor hand hygiene is also a significant factor in its transmission.
Diarrhoea (frequent loose stools) is a symptom of many waterborne diseases. They are caused by biological pollution from human bodily wastes from infected people. Faecal matter contains pathogenic organisms that cause waterborne diseases, mainly diarrhoeal diseases and parasitic worm infections. Some examples of diarrhoeal and other waterborne diseases and their causes are shown in Table 8.1.
Table 8.1 Examples of waterborne disease.
|Viruses||viral gastroenteritis||rotavirus and others|
|viral hepatitis||hepatitis A and E virus|
|Parasitic worms||ascariasis||Ascaris lumbricoides|
|schistosomiasis or bilharzia||Schistosoma|
With one exception, all the diseases in Table 8.1 are caused by people ingesting pathogens by drinking or eating contaminated water or food, or they result from poor hand hygiene. This is faecal–oral transmission which means people are infected with disease when pathogens from faeces enter their body through the mouth. The exception is schistosomiasis, which is caused by worms penetrating the skin when people are swimming or washing in water that has been contaminated with excreta from an infected person.
Chronic health effects of water pollution
Humans are susceptible to the chronic health effects of chemical pollutants if they regularly consume contaminated water or food, especially by eating fish that have lived in polluted water. The process of bioaccumulation can lead to toxic levels of pollutants in fish which, when eaten, lead to damaging levels of toxins in humans. We will illustrate this effect using a historical event that took place in Japan.
Case Study 8.1 Minamata Bay, Japan, 1951
Japan was recovering from an economic crisis in the 1940s after being defeated in the Second World War and was expanding its chemical industries. The Chisso Chemical Corporation had been operating in Minamata since 1932, but had introduced a new manufacturing process using inorganic mercury in 1951. The mercury was released into the sea with wastewater at nearby Minamata Bay. The inorganic mercury was biodegraded and changed into organic mercury, a form that was readily absorbed by fish. Biomagnification of the organic mercury took place in the food chain and led to very high concentrations in the bodies of fish and shellfish.
These fish and shellfish were eaten by the local Japanese people as part of their normal diet. Public complaints started in 1956 as serious damage to people’s health started to be seen. People had symptoms indicating damage to the nervous system (Figure 8.7). There was also damage to the sea environment and other animals such as pigs, cats, dogs and birds that ate contaminated fish. Early studies in 1956 made the link to consumption of fish by victims and suggested the cause was heavy metal contamination (Hachiya, 2006). Factory waste from the Chisso Corporation was suspected, but it was difficult to prove. The government and the factory denied the pollution was due to mercury discharges for many years, and mercury continued to be released into the environment. It was not until 1968 that the government officially recognised that the cause of ‘Minamata disease’ was mercury poisoning. It took 12 years, and many protests and lawsuits before the pollution was stopped. By 2001, of the 2955 victims who had been officially certified and paid compensation, many had died (Ministry of Environment, 2002), although many thousands more had been affected (Hachiya, 2006).
(Adapted from Cunningham and Cunningham, 2011)
What can we learn from the Minamata story? Although the source was suspected, it still took 12 years before it was recognised. The government and the company denied responsibility, and we may suspect a political and economic motive for their refusal to recognise the problem for more than ten years, despite the evidence. We can also see that pollutants can enter the human body through complex routes. The mercury changed its form after it was released into the bay, making it harder to trace. It was not put straight into human food but entered it by bioaccumulation through the food chain from micro-organisms, through small fish to bigger fish.
Another important point from this example is whether the generator of waste is responsible for the waste that they produce, the pollution that they cause in the environment and for the harm caused by that pollution. In this example, the pollution was traced back to the polluter, and compensatory payment was made. However, it took a long time, and some think that payment was not adequate for the damage caused.